Color photographic process using a bleach-fix solution containing a selenosulfate

ABSTRACT

THIS APPLICATION DESCRIBES A COLOUR DEVELOPMENT PROCESS FOR COLOUR SILVER HALIDE PHOTOGRAPHIC MATERIAL, WHEREIN THE MATERIAL AFTER DEVELOPMENT IS TREATED WITH A BLEACHFIX SOLUTION WHICH CONTAINS A MILD OXIDISING AGENT, A SILVER HALIDE SOLVENT AND AS A BLEACH-FIX ACCELERATOR A WATERSOLUBLE SPECIFIED SELENOSULFATE.

United States Patent Oflice 3,702,247 Patented Nov. 7, 1972 3,702,247 COLOR PHOTOGRAPHIC PROCESS USING A BLEACH-FIX SOLUTION CONTAINING A SELENOSULFATE Alun Trefor Rhys Williams and David Gerald Alcock, Ilford, England, assignors to Ilford Limited, Ilford, Essex, England No Drawing. Filed Jan. 12, 1971, Ser. No. 105,955 Claims priority, application Great Britain, Jan. 13, 1970, 1,616/70 Int. Cl. G03c 7/00 US. Cl. 96-55 9 Claims ABSTRACT OF THE DISCLOSURE This application describes a colour development process for colour silver halide photographic material, wherein the material after development is treated with a bleachfix solution which contains a mild oxidising agent, a silver halide solvent and as a bleach-fix accelerator a watersoluble specified selenosulfate.

This invention relates to the processing of photographic material comprising silver halide emulsion layers to yield material having colour dye images therein.

In the processing of conventional colour photographic material a developable silver salt image is developed with an aromatic primary amino developing agent of the paraphenylene diamine type (a so-called colour developer) in the presence of a compound (a so-called colour coupler) which will combine with the oxidation products of the color developer to form an azomethine or quinone-imine dye. The dye is thus formed in situ with the developed silver image. Subsequently the product must be treated with a bleach bath and a fixing bath or a combined bleach-fix bath thereby to remove silver and any residual silver halide or other silver salt, leaving in the product only the dye image.

In the silver-dye-bleach process of colour photography the photographic material comprises at least one silver halide emulsion layer which includes as a dispersion therein an organic dyestulf of the type which can be destroyed (or bleached) by finely divided silver in a suitable treatment bath. The organic dyestulf is usually an azo dye. Most commonly three such silver halide emulsion layers are present each of which is sensitive to a different region of the visible spectrum and each of which contains a different azo dye. The usual processing sequence for the production of a dye image in the material is after an imagewise exposure to develop the material in a black and white developer. The development is then stopped and the unexposed silver halide is fixed out. Then after washing the material is treated in a dye-bleach bath which oxidises the silver image and simultaneously reduces (bleaches) the dye in the region of the silver image. The silver salts and any residual silver must then be removed. This is usually accomplished by washing the material after its treatment in the dye-bleach bath and then treating it in a bleach bath followed by a fixing bath or treating it in a combined bleach-fix bath. The photographic material then contains a dye image only; this dye image being usually a direct positive reproduction of the original.

In one commercially available silver-dye-bleach material the amount of residual silver left after the dyebleach step is not negligible because this material requires to be processed so that the dye-bleach step is terminated before all the image silver has been used in reducing the dye. Thus in the processing of this silver-dyebleach material in particular it is essential that an effective silver bleach step succeeds the dye-bleach step in order to ensure that the residual silver is removed as completely as possible from the material.

In both the processing of conventional colour photographic material and in the processing of silver-dyebleach material the use of a combined bleach-fix bath is preferable because it results in a reduction of the processing time and of the cost of processing equipment required. Normally a bleach-fix bath comprises a mild oxidising agent for example a ferric chelate complex, a cup'ric complex a salt or a cobalt (III) complex together with a silver halide solvent or fixing agent for example a water-soluble thiosulphate or a water-soluble thiocyanate. Strong oxidising agents cannot be used because they tend to oxidise the silver halide solvent.

Sta'ble bleach-fix solutions comprising ferric chelate complexes and sodium thiosulphate may be obtained but because of the weak oxidising power of the ferric chelate complex such bleach-fix baths can only be used commercially for the processing of photographic materials with a fairly low silver content.

According to the present invention in the processing of colour photographic material comprising silver halide emulsion layers to yield material having colour dye images therein there is provided a bleach-fix step which comprises treating the photographic material with a stable bleach-fix bath which comprises an aqueous solution of a mild oxidising agent and a silver halide solvent which is either a water-soluble thiosulphate or a water-soluble thiocyanate in the presence of a bleach-fix accelerator which is a water-soluble selenosulphate of the general formula MSeSO where M is a divalent metal ion, or two monovalent meta ions, or two quarternary ammonium groups or two substituted quaternary ammonium groups.

By stable bleach-fix bath which comprises an aqueous solution of a mild oxidising agent and a silver halide solvent is meant a bleach-fix bath wherein the oxidising agent is strong enough to bleach the silver but is not strong enough to oxidise the silver halide solvent, i.e. the thiocyanate or the thiosulphate, to an appreciable degree.

The preferred mild oxidising agents for use in the present invention are ferric chelate complexes or diaquotetrammine-cobalt (III) complexes.

By ferric chelate complex is meant a co-ordination compound of the ferric ion and a compound which comprises nitrogen and/or oxygen-containing co-ordinating groups. The most important co-ordinating groups are amino, heterocyclic nitrogen, carboxyl and carbonyl groups.

The preferred ferric chelate complex for use in the bleach-fix step of the present invention is a ferric ethylenediaminetetraacetic acid complex. Itis to be understood that this compound may be used as such in the preparation of a bleach-fix bath or it may he formed in situ in a bleach-fix bath by ethylenediaminetetraacetic acid reacting with a ferric salt e.g. ferric chloride. In the examples which follow the ferric ethylenediaminetetraacetic acid complex has been formed in situ.

Other ferric chelate complexes which may be used in the present invention are for example pyridine-2:6-dicarboxylatoferrate (III) complex, iminodiacetatoferrate (III) complex and nitrilo-triacetateferrate (III) complex.

The alkali metal selenosulfates may be prepared by dissolving elemental selenium in alkaline sulphite solution. Crystalline alkali metal selenosulphate may be obtained from this solution or this solution may be used as such, i.e. a quantity of this solution may be added to the bath which is to contain the selenosulphate.

The bleach-fix accelerators of use in the present invention are preferably added to the bleach-fix bath but they may be present during the bleach-fixing treatment adsorbed to or absorbed in the colour photographic material. In the processing of conventional colour photographic material i.e. colour negative or colour reversal material the bleach-fix accelerators of use in the present invention may be present in any treatment bath or wash bath which is used in the colour development process between the development step and the bleach-fix step. Exemplary of such baths are stop baths and stop-fix baths. The bleach-fix accelerators should not be present, however, in the developing solution as they interfere with the development of the colour material. For the same reason the bleach-fix accelerators of use in the present invention should not be present initially in the photographic material.

In the processing of silver-dye-bleach material the bleach-fix accelerators may be present in the wash bath which succeeds the dye-bleach treatment bath and precedes the bleach-fix bath but the bleach-fix accelerators should not be present during the dye-bleach treatment as they can interfere with this treatment step. Thus the bleach fix accelerators should not be present initially in the silver-dye-bleach photographic material.

According to another embodiment of the present invention there is provided a stable bleach-fix bath which comprises a mild oxidising agent, as hereinbefore defined, a silver halide solvent which is either a water-soluble thiosulphate or a water-soluble thiocyanate and a water-sob uble selenosulphate as a bleach-fix accelerator.

Preferably in this aspect of the invention the mild oxidizing agent is a ferric chelate complex or a diaquotetramine-cobalt (III) complex.

It is preferred that the concentration of selenosulphate present in the bleach-fix bath is greater than 1 g. per litre of bleach-fix bath. The most preferred amount being g. of bleach-fix accelerator per litre of bleach-fix bath.

The following examples will serve to illustrate the invention.

EXAMPLE 1 In this example a colour negative film was used, which was made up as follows:

Layer order and Silver coating weight in sensitivity: mg. of Ag/decimetre Non Blue sensitive 13.4 Colloidal silver filler layer Green sensitive topcoat 13.1 Intralayer Green sensitive subcoat 16.0 Interlayer Red sensitive topcoat 175 Red sensitive subcoat 13.6

Base of cellulose triacetate Total 73.6

In this film: the blue sensitive layer contained a yellow colour coupler of the formula:

N-C Ha the green sensitive layers each contained a magenta colour coupler of the formula:

@ Q (ii-Ca as 0 the red sensitive layers each contained a cyan colour coupler for the formula:

Cg: /C1sHa1 OH I? l C ONH COzH Samples from a batch of this colour negative tripack material (which is of the colour coupler substantive type) containing 73.6 mg. of silver per dm. as silver iodobromide emulsion were fogged and processed at 24 C.

The processing sequence was:

Colour development: 6 minutes G. Sodium metaborate 53.3 Sodium hydroxide 2.0 Sodium sulphite anhydrous 3.9 Potassium bromide 0.70 Hydroxylamine sulphate 2.34 Sodium sulphate anhydrous 7.8 4 amino N ethyl N (4 hydroxybutyl) aniline sulphate Water to 1 litre. pH 10.5.

Stop-fix: 4 minutes Sodium thiosulphate pentahydrate g 171.0 Sodium acetate anhydrous g 31.4 Sodium sulphite anhydrous g 4.3 Acetic acid (glacial) ml Potassium alum g 17.0 Ammonium chloride g 43.0 Water to 1 litre. pH 4.3.

Wash: 4 minutes Bleach-fix: minutes Disodium tetraborate decahydrate g 12.5 Boric acid g 22.5 Sodium hydroxide g 10.0 Ethylene diaminetetraacetic acid g 16.2 Disodium salt of ethylenediaminetetraacetic acid dihydrate g 3.5 Ferric chloride w./v. soln.) ml 15 Sodium thiosulphate pentahydrate g 95.0 Sodium sulphite anhydrous g 4.0 Magnesium sulphate g 12.5 Water to 1 litre. pH 7.0. Wash: 4 minutes Conditioner: 4 minutes Disodium salt of ethylenediaminetetraacetic acid dihydrate g 0.50 Sodium carbonate anhydrous g 4.5 Formaldehyde (40% w./v. soln.) ml 10 Lissapol N (8% w./v. soln.) ml 1.7 Water to 1 litre. pH 10.7.

Wash: 4 minutes Dry CHzOCOCzH In this test a bleach-fix time of 45 minutes was required before all the residual silver had cleared from the film. This is referred to as the clearing time.

In another test samples of the same negative film were fogged and processed as above except for the bleach-fix stage where g. of crystalline sodium selenosulphate were added to the bleach-fix bath described above. In these tests an average clearing time of only 10 minutes was required before all the residual silver had cleared from the film. Thus the sodium selenosulphate has accelerated considerably the bleach-fix process.

EXAMPLE 2 A positive tripack colour material intended for the silver dye-bleach system comprising silver halide emulsions containing bleachable azo-dyes Cibachrome manufactured by Ciba-Geigy A.G. of Switzerland was given a neutral wedge exposure and processed, the processing sequence being as follows:

Development: 10 minutes p-Methyl-aminophenol-sulphate 1 Sodium sulphite anhydrous 20 Hydroquinone 4 Sodium carbonate anhydrous 10 Potassium bromide 2 Water to 1 litre.

Stopfix: 4 minutes G. Sodium thiosulphate pentahydrate 200 Sodium sulphite anhydrous 20 Water to 1 litre.

Wash: 8 minutes Dye-bleach: 20 minutes Sulphuric acid, 96% ml 27.5 Potassium iodide g 10 Solution of 0.3 g. 2,3-dimethyl-6-aminoquinoxaline in 50 ml ethnol ml Water to 1 litre.

Wash: 4 minutes Bleach-fix: 10 minutes Disodium tetraborate decahydrate -g 12.5 Boric acid g 22.5 Sodium hydroxide g 10.0 Ethylenediaminetetraacetic acid g 16.2 Disodium salt of ethylenediaminetetraacetic acid dihydrate -g 3.5 Ferric chloride (60% W./v. soln.) ml 15 Sodium thiosulphate pentahydrate g 95.0 Sodium sulphite anhydrous g 4.0 Sodium selenosulphate g 10 Water to 1 litre. Wash: 8 minutes Dry The processed material was satisfactory and substantially no residual silver was left in the material even in the areas of high exposure. Similar silver-dye-bleach material was exposed and processed using the same solutions as set forth above except that the bleach-fix solution contained no sodium selenosulphate. Even when the material had been treated in the bleach-fit bath for 25 minutes it was unsatisfactory because it had a high minimal density due to the incomplete removal of the residual silver in 116 areas of high exposure.

We claim as our invention:

1. In the processing of colour photographic material comprising silver halide emulsion layers to yield material having colour dye images therein the step of treating the photographic material with a stable bleach-fix bath which comprises an aqueous solution of a mild oxidising agent and a silver halide solvent which is either a water-soluble thiosulphatc or a water-soluble thiocyanate in the presence of a bleach-fix accelerator which is water-soluble selenosulphate of the formula MSeSO where M is two sodium ions, said oxidising agent being one which is strong enough to bleach the silver but is not strong enough to oxidise the silver halide solvent.

2. A process according to claim 1 wherein the mild oxidising agent is a ferric chelate complex.

3. A process according to claim 2 wherein the ferric chelate complex is ferric ethylenediaminetetraacetic acid complex.

4. A process according to claim 1 wehrein the bleachfix accelerator is present in the bleach-fix bath.

5. A stable bleach-fix bath which comprises an aqueous solution of a mild oxidising agent, a silver halide solvent which is either a water-soluble thiosulphate or a water-soluble thiocyanate and a water-soluble bleach-fix accelerator which is a selenosulphate of the general formula MSeSO where M is two sodium ions, said oxidising agent being one which is strong enough to bleach the silver but is not strong enough to oxidise the silver halide solvent.

6. A stable bleach-fix bath according to claim 5 wherein the mild oxidising agent is a ferric chelate complex.

7. A stable bleach-fix bath according to claim 6 wherein the ferric chelate complex is ferric ethylenediaminetetraacetic acid complex.

8. A stable bleach-fix bath according to claim 5 wherein the concentration of bleach-fix accelerator is greater than 1 g. per litre of bleach-fix bath.

9. A stop-fix bath which comprises an aqueous acid solution of a silver halide solvent selected from a watersoluble thiosulphate or a water-soluble thiocyanate and a water-soluble bleach-fix accelerator which is a selenosulphate of the general formula MSeSO where M is two sodium ions.

References Cited UNITED STATES PATENTS 2,770,542 11/1956 Burt 9657 3,189,452 6/1965 Bard et al 9656 3,619,188 11/1971 Alcock et a1. 9660 BF J. TRAVIS BROWN, Primary Examiner U.S. Cl. X.R. 9660 BF, 61 R, 62 

